1. Field of the Invention
Aspects of the present invention relate to a secondary battery, and more particularly, to a protection circuit module of a secondary battery by which an assembling workability of the battery is enhanced and manufacturing costs can be reduced and a secondary battery using the same.
2. Description of the Related Art
Recently, secondary batteries have become widely employed in electronic products due to their rechargeability, small size, and large capacities. The secondary batteries are classified into various groups, including nickel hydrogen batteries, lithium batteries, lithium ion batteries, etc. The secondary battery is configured to include an electrode assembly and an electrolyte accommodated in a can, and electrode taps extended from electrode plates of the electrode assembly to connect to external terminals of a case. The electrode assembly includes a positive electrode plate and a negative electrode plate insulated from each other by a separator. Furthermore, in the secondary battery, a safety device (such as a positive temperature coefficient (PTC) device) is installed at a side of the secondary battery to prevent an accident such as explosion, burning, etc., from occurring due to an increase of an inner pressure when the secondary battery is exposed to a high temperature or a high voltage.
Specifically, the PTC device cuts off current when an electric device is exposed to high temperature. Although the PTC device is applied to various electronic devices, when employed in the battery, the PTC device plays a role of a safety device to prevent a battery from being exploded or burnt due to high temperature. The PTC device is made of a mixture of polymer and conductive material to be conductive. When the PTC is exposed to a high temperature such that the temperature of the PTC device is increased, the polymer expands and contacts between conductive particles are cut off so that resistance is suddenly increased to cut off the current.
For example, the PTC device installed in the secondary battery includes a PTC main body and conductive terminals connected to ends of the PTC main body. The PTC device is installed to an upper side or a lower side of a bare cell of the secondary battery. Furthermore, one terminal of the PTC device is connected to one electrode of the electrode assembly and the other terminal is connected to the external terminal via a protection circuit module. In this case, the terminals of the PTC device are electrically connected to the electrode terminals or the protection circuit module in a state of being connected to a lead plate. Accordingly, a conventional connecting structure between terminals for installation of the PTC device is complicated, and workability is thus inferior. Additionally, since the lead plate and an insulation material are required for the installation of the PTC device, a number of components are needed and manufacturing costs increase.